On December 14th, Prof. Harold Metcalf from the department of Physics & astronomy at Stony Brook University visited SIOM for academic exchange and gave a high-level presentation at Qinghe Seminar. Prof. LIU Liang, director of Key Laboratory of Quantum Optics, CAS presided over the seminar. About 50 researchers and students participated the seminar. On Qinghe Seminar, Prof. Harold Metcalf gave a report entitled “Optical Forces in non-Monochromatic Light”. In his report, he first reviewed the laser cooling. The simple model of a frequency of light acting on a two-level atom provided descriptions of beam slowing, optical molasses, optical traps, and a host of other phenomena. However, not all experiments could be described by this simple, two-level model. Then he expanded to a multilevel atom description led Sisyphus cooling, magneto-optical traps, velocity selective coherent population trapping, and many other things. He explained the dressed atom, the bichromatic force and a coherent state view. In the end, he introduced polychromatic light acting on a two level atoms. After the seminar, Ms. LIN Hongxiang, on behalf of SIOM, awarded the Prize of Qinghe Seminar to Prof. Harold Metcalf. Following the seminar, Prof. Harold Metcalf paid a visit to the Key Laboratory of Quantum Optics, CAS. Dr. Harold Metcalf is a distinguished teaching professor in the department of Physics & astronomy at Stony Brook University. He is one of the pioneer of laser cooling, a technique in which a laser beam is shined on atoms and cools them down to temperatures of microkelvins, where quantum mechanical properties can be experimentally observed. In fact, he and a colleague wrote the book in it, “Laser Cooling and Trapping,” published in 1999. His role in the development of this vital scientific is considered so significant that when William D. Phillips was jointly awarded the Nobel Prize in physics in 1997 for “development of methods to cool and trap atoms with laser light,” he recognized Metcalf in his Nobel autobiography. More recently, he focused on ultra-strong optical forces with a huge velocity capture range provided by non-monochromatic light. These forces were recently exploited for atomic nanofabrication and cooling without spontaneous emission. He has published over 150 refereed papers, several review papers, the widely used Laser Cooling book, and their new book on atomic physics.